An image forming apparatus for electrophotographic image formation includes various power supply members to which high voltage power is supplied, such as a transfer roller, a charger, or a developing roller. To these power supplied members, power is supplied from one high voltage power supply substrate provided in an apparatus body of the image forming apparatus.
On the high voltage power supply substrate, a plurality of electrodes electrically connected to the power supplied members are provided, and the electrodes are placed at certain intervals for preventing discharge. Particularly, high voltages are applied to the transfer roller and the charger, the voltages have opposite polarities, and thus the transfer roller and the charger have a large potential difference, which requires large intervals between the electrodes connected to the transfer roller and the charger.